Arrangement for the spectral analysis of substances

Abstract

An arrangement of the Rowland character includes a support and a concave grating on the support for producing the spectrum characteristic of a sample being investigated. The support has a series of slits thereon which are positioned on the Rowland circle and are adjusted to the spectral lines of samples to be investigated. An element on the support is provided with a primary slit for directing the radiation derived from a sample being investigated onto the concave grating. The primary slit is positioned on the Rowland circle and the element provided with the primary slit is mounted on the support for movement along the arc of the Rowland circle. The element is mounted in such a manner as to be arrestable in a plurality of positions. The element is favorably in the form of a plate. A preferred embodiment contemplates the provision of a pair of grooves in the support, which latter may be in the form of a housing, with the grooves following the curvature of the Rowland circle and the element being guided in the grooves. The edges of the element located in the grooves may be provided with openings in which there are accommodated spherical members as well as biasing elements for urging the spherical members into contact with the grooves.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims: 
     
       1. An apparatus for spectroscopically analyzing the composition of a workpiece, comprising a portable support; means including an electrode juxtaposable with a surface of the workpiece for sparking between said surface and said electrode; optical means on said portable support for transmitting into said support the light of a spark between said electrode and said surface; a reflective Rowland grating in said support and defining therein a Rowland circle having a small diameter of about 1/2 meter; an arcuate guide in said portable support conforming to and extending along said Rowland circle; displaceable means defining a primary slit and being positively displaceable along said arcuate guide for casting the light from said optical means onto said Rowland grating; means for positively displacing said primary slit defining means along said arcuate guide exactly circumferentially of said Rowland circle in an arucate path in which said primary slit is always located on the Rowland circle, and for arresting said primary slit on said arcuate guide against displacement due to vibrations and jarring resulting from transportation of said portable support, at any of a multiplicity of offset positions on said guide; and means defining a plurality of spaced-apart secondary slits fixed on said support at said Rowland circle for breaking the light reflected by said Rowland grating down into an analyzable spectrum, whereby the apparatus is portable and at the same time provides for high accuracy of analysis because of the small diameter of said Rowland circle of about 1/2 meter in combination with the positive displacement of said primary slit defining means exactly circumferentially of said Rowland circle and arresting of the same at any of the multiplicity of offset positions. 
     
     
       2. An arrangement as defined in claim 1, wherein said primary slit defining means comprises a plate. 
     
     
       3. An arrangement as defined in claim 1, wherein said support comprises a housing and said primary slit defining means is accommodated interiorly of said housing. 
     
     
       4. An arrangement as defined in claim 1, wherein said guide has a pair of grooves which follow the curvature of the Rowland circle and said primary slit defining means is guided in said grooves. 
     
     
       5. An arrangement as defined in claim 4, said primary slit defining means having an edge located in one of said grooves, and said edge being provided with openings; and wherein spherical members are provided in said openings and at least one biasing element is provided for urging said spherical members into contact with said grooves. 
     
     
       6. The apparatus defined in claim 1; said primary slit defining means comprising a carrier displaceable along said arcuate guide and carrying said primary slit. 
     
     
       7. The apparatus defined in claim 6, wherein said guide has a pair of spaced arcuate sides each formed with a respective arcuate groove opening toward the groove of the other side.